The greater portion of the brain is destitute of sensibility, Sir C. Bell imagines from this that it possesses a higher office than that of sensual perception. The external substance of the brain is arranged in convolutions or folds; these appear to be intended for the purpose of increasing its superficial extent with the least enlargement of size,--in the inferior classes of animals there are no convolutions, but they increase in number and extent as we ascend in the scale of being. Each side of the _brain_ and also of the _cerebellum_, is supplied with separate arteries conveying blood to it, while the _sinuses_ or canals which return the blood to the heart are common to all. The CEREBELLUM is composed of matter similar to that of the brain in appearance, but different in arrangement,--it is separated from the brain by a strong membrane called the _tentorium_: its fibres originate in the _medulla oblongata_ where the organs of the propensities take their rise, so that the _brain and cerebellum_ although separated by the _tentorium_ are both connected together. The brain and Cerebellum are protected by the skull, and the brain is formed before the bones which invest it. The process of ossification is gradual, the principal portion at birth being strong membranes in which the points of ossification begin and continue increasing in extent and strength till about the age of nine years: between the substance of the brain and the skull are the _pia mater_ and the _dura mater_, two integuments which enclose the peripheral extent of the brain and convey blood-vessels to its several parts, the brain with these membranes exactly fills the interior of the skull. The skull fully formed is composed of eight bones which are connected by indented edges: the internal and external surfaces are, from their smooth surface called the _plates_ and the intermediate part, _diploe_, which is of a loose cellular texture; as this _diploe_ is nearly equally thick in every part, the two tables are nearly parallel to each other, and the variations where they occur do not exceed the eighth or tenth part of an inch; the integuments being an exact form of the brain, and the bony matter fitting them exactly, it follows that there is no obstacle of importance to prevent our observing the form of the brain by the form of the skull.